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The paddlewheel aerators run 24 hours a day The ponds are dried and limed after each cycle is completed BARRAMUNDI is a long-term investment BY JOHN MOSIG M arty Phillips is a partner in Pejo Enterprises. They bought the former banana plantation 10km south of Innisfail in Far North Queensland in 2002 and set about diversifying into fi sh farming. It took two costly and frustrating years for the company to get an aquaculture permit, then they had to re-build their sheds after Cyclone Larry, but they are now producing close to 300 tonnes of barramundi a year. Water is drawn from the Moresby River and a bore alongside the nursery and packing shed. The Moresby is a short, coastal river and the catchment in the nearby Basilisk Range can be clearly seen from the farm. This reduces fl ooding in the wet, in a region where the rainfall reaches 3m a year. "Flooding and fi sh farming don't mix," says Marty. The bore water is soft and low in dissolved oxygen, but both conditions can be corrected relatively easily. The temperature is a constant 26˚Celsius. It is heated to 28˚C for use in the nursery. The average summer temperature in the district is 30˚C and the mean winter temperature is 24˚C. Seasonal rain also affects the salinity, which ranges between 25-29ppt. The river is tidal where Marty has built his farm, and during dry spells the tide pushes back against the river fl ow. In the wet the water becomes fresh, even though the tide still pushes back against the fl ow. Marty says it gives his fi sh a salt bath to remove freshwater parasites and a freshwater bath to remove saltwater parasites a couple of times a year. They ship in salt water for the marine stage of the hatchery phase and use the bore water in a semi fl ow-through system once the fry have become acclimatised to fresh water. The 33 ponds on the farm cover 12.6ha and vary in size but are mainly 50m x 80m x 2.5m deep. Two large settlement ponds create a wetland environment for a few crocodiles and thousands of waterfowl, including the endangered Burdekin duck. Pond temperatures range from 22˚C to a summer peak of 36˚C. Aeration per 0.4ha pond is a combination of a 1.5kW paddlewheel and a 1.5kW aerojet, giving coverage of 7.5kW/ha. The property has three-phase power throughout and Marty has a 400kVa diesel back-up generator in place. A re-circulation nursery system handles the barramundi from the time they are day-old larvae until they are 100mm fi ngerlings. This is set up in two stages: saline and fresh water. Food is kept in cold storage and they can hold eight tonnes of chilled fi sh in the coolroom. PRODUCTION CYCLE Pejo Enterprises try to get two batches of day-old barramundi larvae through a year. The larvae are taken in autumn and spring and are in the nursery tanks for 12 weeks, when they are 100mm long. They are inoculated for streptococcus and relocated in cages in the production ponds. After another six to eight weeks they weigh 200-300g and are ready to swim freely in the ponds. It takes another 18 to 20 months for the fi sh to reach three kilos. Marty says they work on a two-year cycle and harvest 20 tonnes per pond, or 50 tonnes per hectare. There are two re-circulation systems: a marine system for larval rearing and a freshwater system to grow the fry on to fi ngerlings. They swap the fry over to fresh water as soon as possible. The re-circulation system isn't sophisticated and has evolved over time. Marty reasons since he has such good quality bore water it's cheaper to increase water exchange when the load demands it, rather than spend huge sums buying and operating bells-and-whistles technology. Water exchange through the re-circulation system is hourly and the water in the system is replenished four to fi ve times a day, depending on the load. Fish are graded twice during the nursery stage and the poorest 20 percent are culled and discarded before they cost too much. The total throughput is 150,000 fry a year. The ponds are drained and dried at the end of each cycle The final stage of the nursery is partially open to help acclimatise the fingerlings before they go out into the cages 6 ■ NZ AQUACULTURE ■ SEPTEMBER/OCTOBER 2011 and ground limestone added at the rate of 2.5 tonnes/ha during the growing cycle as required. Aeration is increased as the pond loads build up until it is twice the normal level close to harvest. Pejo employs two full-time permanent staff and two permanent casuals who have developed into a highly effi cient